The Precision Time Protocol(PTP) of IEEE 802.1AS, IEEE standard 1588, is a synchronization protocol for the precise synchronization of clock times in a network. The Precision Time Protocol ensures that the time bases of all devices and systems connected to the network are synchronized in time with very high accuracy. The synchronization accuracy is in the nanosecond range.
Due to the synchronization, the devices can use unique time stamps and transmit data at defined times. The PTP time protocol is optimized for smaller networks that have few subnets. It is characterized by minimal administrative overhead, low bandwidth requirements and equally low computing power.
The PTP concept works with decentralized clocks that are synchronized with a central time server. The most accurate clock in a network, the Grandmaster Clock, serves as a reference. It forms the master with which the slaves in the network are synchronized. The time server distributes the time reference signal to the subordinate clocks, the Ordinary Clocks, which evaluate it. From the propagation time of the time stamps from the reference clock to the subordinate clocks and back, the delay and processing time of the time stamps can be calculated and the time information of the subordinate clocks can be corrected accordingly. Thus, exact equality between reference clock and subordinate clocks can be established.
With the Precision Time Protocol, time references from atomic clocks or from the GPS system can be distributed with the exact, absolute time and highest accuracy to all stations connected in the network.
Important areas of application for the PTP time protocol are industrial automation, automated measurement technology and measurement data acquisition, in which the measurement data is acquired at a specified time, provided with a time stamp and transmitted. Other areas of application are IP-basedreal-time communication in automation and automotive technology, wide area networks with their switches and routers and, last but not least, audio-videobridging( AVB).